Sql interview questions – javatpoint

There is given sql interview questions and answers that has been asked in many companies. Cnet data recovery For PL/SQL interview questions, visit our next page. Database systems 1) What is SQL?

SQL stands for structured query language. Data recovery for mac It is a database language used for database creation, deletion, fetching rows and modifying rows etc. Data recovery damaged hard drive sometimes it is pronounced as se-qwell.


Database builder 2) When SQL appeared?

Data definition language(DDL) allows you to CREATE, ALTER and DELETE database objects such as schema, tables, view, sequence etc. Data recovery cnet 7) What is data manipulation language?

A table contains specified number of column called fields but can have any number of rows which is known as record. Database log horizon 10) What is a primary key?

A primary key is a combination of fields which uniquely specify a row. Data recovery raid This is a special kind of unique key. Database design for mere mortals Primary key values cannot be NULL. Database hardening 11) What is a foreign key?

A foreign key is specified as a key which is related to the primary key of another table. Data recovery linux distro Relationship needs to be created between two tables by referencing foreign key with the primary key of another table. Data recovery key 12) What is a unique key?

A Unique key constraint uniquely identifies each record in the database. Data recovery macbook This provides uniqueness for the column or set of columns. Data recovery los angeles 13) What are the type of operators available in SQL?

A view is a virtual table which contains a subset of data within a table. Database yml Views are not virtually present, and it takes less space to store. Database in excel View can have data of one or more tables combined, and it is depending on the relationship. G info database 15) What is an Index in SQL?

Index is used to increase the performance and allow faster retrieval of records from the table. Database book An index creates an entry for each value and it will be faster to retrieve data. Q prime database 16) Which are the different types of indexes in SQL?

This indexing does not allow the field to have duplicate values if the column is unique indexed. Top 10 data recovery tools Unique index can be applied automatically when primary key is defined. Data recovery laptop 18) What is Clustered Index in SQl?

The clustered index is used to reorder the physical order of the table and search based on the key values. Data recovery flash drive Each table can have only one clustered index. Data recovery cost 19) What is NonClustered Index in SQL?

NonClustered Index does not alter the physical order of the table and maintains logical order of data. Data recovery galaxy s5 Each table can have 999 non-clustered indexes. Database key field 20) What is the difference between SQL, MySQL and SQL Server?

SQL or Structured Query Language is a language which is used to communicate with a relational database. Data recovery nashville It provides a way to manipulate and create databases. Data recovery minneapolis On the other hand, MySQL and Microsoft’s SQL Server both are relational database management systems that use SQL as their standard relational database language. Database 4 net 21) What is the difference between SQL and PL/SQL?

SQL or Structured Query Language is a language which is used to communicate with a relational database. Iphone 6 data recovery software free It provides a way to manipulate and create databases. Database usa reviews On the other hand, PL/SQL is a dialect of SQL which is used to enhance the capabilities of SQL. Easeus data recovery 94fbr It was developed by Oracle Corporation in the early 90’s. Database join It adds procedural features of programming languages in SQL. H2 database download 22) Is it possible to sort a column using a column alias?

Yes. H2 database url You can use column alias in the ORDER BY clause for sorting. Data recovery boot disk 23) What is the difference between clustered and non clustered index in SQL?

There are mainly two type of indexes in SQL, Clustered index and non clustered index. 990 database The differences between these two indexes is very important from SQL performance perspective.

• clustered index determines how data is stored physically in table. Data recovery hard drive cost Actually clustered index stores data in cluster, related data is stored together so it makes simple to retrieve data.

• clustered index sort and store data rows in the table or view based on their key value, while non cluster have a structure separate from the data row.

There is a built in function in SQL called GetDate() which is used to return current timestamp. Data recovery knoxville 25) Which are the most commonly used SQL joins?

Right join is used to retrieve rows which are common between the tables and all rows of Right hand side table. 7 data recovery keygen It returns all the rows from the right hand side table even though there are no matches in the left hand side table. H2 database client 29) What is Left Join in SQL?

Left join is used to retrieve rows which are common between the tables and all rows of Left hand side table. Dayz database It returns all the rows from Left hand side table even though there are no matches in the Right hand side table. I phone data recovery 30) What is Full Join in SQL?

Full join return rows when there are matching rows in any one of the tables. Database 3d This means, it returns all the rows from the left hand side table and all the rows from the right hand side table. Yorku database 31) What is “TRIGGER” in SQL?

Actually triggers are special type of stored procedures that are defined to execute automatically in place or after data modifications. O o data recovery 32) What is self join and what is the requirement of self join?

Self join is often very useful to convert a hierarchical structure to a flat structure. Data recovery illustrator It is used to join a table to itself as like if that is the second table. Database management software 33) What are set operators in SQL?

The BETWEEN operator is used to display rows based on a range of values. Database normalization example The IN condition operator is used to check for values contained in a specific set of values. Database virtualization 35) What is a constraint? Tell me about its various levels.

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